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<html lang="en">
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    <title>Document</title>
    <script src="../vue.js"></script>
</head>
<body>
    <!-- 
        深度监视:
            (1).Vue中的watch默认不监测对象内部值的改变(一层)
            (2).配置deep true可以检测对象内部值改变(多层)
        备注:
            (1).Vue自身可以监测对象内部值的改变,但Vue提供的watch默认不可以
            (2).使用watch时根据数据的具体结构,决定是否采用深度监视
     -->
    <div id="root">
        <h2>今天天气很{{info}}</h2>
        <button @click="changeWeather">切换天气2</button>
        <br>
        <h3>a的值是{{numbers.a}}</h3>
        <button @click="numbers.a++">点我让a+1</button>
        <h3>b的值是{{numbers.b}}</h3>
        <button @click="numbers.b++">点我让b+1</button>

        <button @click="numbers={a:111,b:222}">彻底替换numbers</button>
    </div>

    <script>
        Vue.config.productionTip = false
       const vm = new Vue({
            el: '#root',
            data: {
                isHot: true,
                numbers: {
                    a:1,
                    b:1
                }
            },
            computed: {
                info () {
                    return this.isHot?'炎热' : '凉爽' 
                }
            },
            methods: {
                changeWeather () {
                    this.isHot = !this.isHot
                }
            },
            watch: {
                isHot: {
                    handler (newValue, oldValue) {
                        console.log('isHot被修改了')
                        console.log('新的值:', newValue)
                        console.log('旧的值:', oldValue)
                    }, 
                },
                //监视多级结构中某个属性的变化
                'numbers.a': {
                    handler (newValue, oldValue) {
                        console.log('a+1')
                        console.log('新的值:', newValue)
                        console.log('旧的值:', oldValue)
                    }, 
                },
                //监视多级结构中所有属性的变化
                numbers: {
                    deep: true,
                    handler () {
                        console.log('numbers改变了')
                    }
                }
            }
        })


    </script>
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